Posterolateral protrusion of the vertebral artery over the posterior arch of the atlas: quantitative anatomical study using three-dimensional computed tomography angiography

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The vertebral artery (VA) often takes a protrusive course posterolaterally over the posterior arch of the atlas. In this study, the authors attempted to quantify this posterolateral protrusion of the VA.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Three-dimensional CT angiography images obtained for various cranial or cervical diseases in 140 patients were reviewed and evaluated. Seven patients were excluded for various reasons. To quantify the protrusive course of the VA, the diameter of the VA and 4 parameters were measured in images of the C1–VA complex obtained in the remaining 133 patients. The authors also checked for anomalies and anatomical variations.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>When there was no dominant side, mean distances from the most protrusive part of the VA to the posterior arch of the atlas were 6.73 ± 2.35 mm (right) and 6.8 ± 2.15 mm (left). When the left side of the VA was dominant, the distance on the left side (8.46 ± 2.00 mm) was significantly larger than that of the right side (6.64 ± 2.0 mm). When compared by age group (≤ 30 years, 31–60 years, and ≥ 61 years), there were no significant differences in the extent of the protrusion. When there was no dominant side, the mean distances from the most protrusive part of the VA to the midline were 30.73 ± 2.51 mm (right side) and 30.79 ± 2.47 mm (left side). When the left side of the VA was dominant, the distance on the left side (32.68 ± 2.03 mm) was significantly larger than that on the right side (29.87 ± 2.53 mm). The distance from the midline to the intersection of the VA and inner cortex of the posterior arch of the atlas was ~ 12 mm, irrespective of the side of VA dominance. The distance from the midline to the intersection of the VA and outer cortex of the posterior arch was ~ 20 mm on both sides. Anatomical variations and anomalies were found as follows: bony bridge formation over the groove for the VA on the posterior arch of C-1 (9.3%), an extracranial origin of the posterior inferior cerebellar artery (8.2%), and a VA passing beneath the posterior arch of the atlas (1.8%).</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>There may be significant variation in the location and branches of the VA that may place the vessel at risk during surgical intervention. If concern is noted about the vulnerability of the VA or its branches during surgery, preoperative evaluation by CT angiography should be considered.</jats:p></jats:sec>

Course variability of the atlantic (V3) segment of vertebral artery: anatomical study with clinical implications

“…These discrepancies may originate from subjective observations of the course of the VA, which are difficult because of waveform shape of the artery and oblique axis of the atlanto-occipital joint. On the other hand Yamaguchi et al [16] in study based on the large radiological material pointed the postero-lateral protrusion of the VA over the posterior arch of atlas. In the material studied for this paper we found wide range of shapes of the V3 arch, where wide arches with initially postero-lateral course prevail.…”

Quantitative Anatomical Study of Tailored Far-Lateral Approach for the VA-PICA Regions

“…The location of neurovascular structures in the VA-PICA region can vary significantly. 5,34,35 Awareness of the presence of anatomical variations is important for performing these procedures safely. Care should be taken to identify important vital structures including the anterior and posterior spinal artery and the perforating arteries to the brainstem.…”

Multiple symptomatic vertebral artery loops treated with posterior cervical fusion

“…1 These abnormal vessels can be located anywhere in the cervical spine including C1 and C2. 2,3 In the subaxial spine the C4/5 level is the most common location for these lesions followed by C3/4 and C5/6. 4 Clinically, these uncommon lesions can present with a spectrum of symptoms ranging from asymptomatic states, which are discovered incidentally, to radiculopathy, 4-6 vertebrobasilar insufficiency, and/or stroke syndromes.…”